It's an odd place for a kitchen chair, but I imagine the camera dept put it there just to fill in the blank space.
I love the random appearances of The Bradys living room televison set. Perhaps it was put there for the same reason.
Rather than mirroring the counter culture protests of the 60s and 70s against wars, and civil rights directly, these sitcoms usually took a safer, less contoversial stance by protesting things like the closing of parks and the unfair removal of trees.